Apparatus for analyzing thin film property

Abstract

A method and apparatus for measuring electrical characteristics of a thin surface layer of a sample such as a semiconductor element. A triangular pulse wave of is applied between the sample and a probe needle on a cantilever. By measuring current that flows through the thin surface layer of the sample using the probe needle, I/V characteristics are obtained. A control circuit keep constant the clearance between the probe needle and the thin surface layer of the sample by applying a voltage to a piezoelectric element that supports the sample. I/V characteristics are then measured at a plurality of test points on the thin surface layer of the sample.

What is claimed is: 
     
       1. An apparatus for analyzing a property of a thin film comprising: measuring means for measuring an I/V characteristic of a thin film disposed on a sample, at each of a plurality of test points on the thin film, the measuring means including: means for applying a voltage V increasing with time to a maximum voltage across a probe spaced from the thin film and the thin film;   means for detecting a current I flowing between the probe and the thin film in response to the voltage;   means for switching the voltage to zero when the current detected by the means for detecting exceeds a threshold current before the voltage reaches the maximum voltage for preventing excessive current from flowing between the thin film and the probe whereby damage to the probe is avoided; and   means for moving the thin film relative to the probe for sequentially and respectively placing the probe opposite each of the test points; and     image forming means for forming a surface current distribution image based on the I/V characteristic measured at each of the test points by the measuring means.   
     
     
       2. The apparatus according to claim 1 wherein the measuring means also measures surface roughness at each of the plurality of test points, and the image forming means forms a surface roughness image based on the surface roughness measured by the measuring means. 
     
     
       3. The apparatus according to claim 2 wherein the measuring means includes an atomic force microscope and the probe comprises a cantilever having a needle on one end, the atomic force microscope including a feedback loop for maintaining a constant separation between the needle and the thin film, and feedback switching means for opening the feedback loop during measurement of an I/V characteristic. 
     
     
       4. The apparatus according to claim 3 including an electrically conductive coating having a high melting point and disposed on the cantilever and the needle.